Figure 6. Simulated spinal network of the pathway from skin to ipsi- and contralateral motoneurons seen in dorsal view.

Skin stimulation can excite 1–5 sensory RB neurons. These project (200 μm) into the spinal cord where their longitudinal axons synapse with up to 60 dlc interneurons (dlc INs) and 15 dl interneurons (dl INs). dlc interneurons are more closely spaced (mean, 23 μm) and project across the spinal cord (157 μm) where they can ascend or descend to synapse with the contralateral motoneuron (mn). dl interneurons are more widely spaced (mean, 43 μm) and project ventrally on the same side (78 μm) then ascend to synapse with the ipsilateral motoneuron. The position of the jth dlc interneuron and the kth dl interneuron were specified relative to the recorded motoneuron (either contralateral or ipsilateral). More details in text and Tables 1 and 2.